Arrangements of NTC resistors on electromagnets are known. They serve for temperature compensation when magnetic coils with a strong variation of thermal stress are used. The electromagnetic coils usually comprise a main winding and a shunt winding wound together on the coil carrier, wherein the NTC resistor is connected in parallel with the shunt winding and this circuit is connected in series with the main winding, or the NTC resistor is connected in series with the shunt winding and this circuit is connected in parallel with the main winding. This temperature compensation is necessary since temperature variations between about −30° C. to about 150° C. exist for a magnetic coil used in a motor vehicle. The magnetic force of the coil drops as the temperature rises, the drop being due to the temperature-dependent resistance of the coil wire. This is compensated for by the use of the NTC resistors, by means of which it is achieved that the same magnetic force is generated at the coil when the pulse-width modulated signal at the contact terminals is the same.
The use of such NTC resistors is described, for example, in DE 42 05 563 A1. Here the NTC resistor is arranged in the power supply with a shunt coil being connected in parallel therewith. This is to additionally improve the consistency of the magnetic force for equal control signals. The mounting of the resistor is not part of the subject matter of this application.
The NTC resistors used in such circuits are produced as standardized components with soldered contact wires. These contact wires are typically first bent and are then soldered to contacts of the coil. The solder used either includes lead or has a melting temperature that is insufficient for production-related reasons.
Known NTC resistors have the drawbacks that sufficient strength of the connection of the NTC resistor to the contacts of the electromagnetic coil often does not exist and environmentally hazardous materials must be used. Both the required vibration resistance and the temperature resistance of the known connections is furthermore often insufficient.